Lubricating compositions inhibited from oxidation

ABSTRACT

A lubricating composition of mineral oil or synthetic oil is inhibited from oxidation by dissolving therein, at temperatures not higher than 80* C, from 0.001 to 10 per cent by weight of a derivative of thio-thiophthene which is represented by the general formula: WHEREIN R, R1, R2 and R3, which may be the same or different, are members of the group consisting of hydrogen, alkyl, cycloalkyl, aryl, alkylaryl, arylalkyl, alkoxyaryl, alkoxyalkyl, and aroxyalkyl, or R2 and R3 are combined and together represent an alkylene radical of the -CH2 - type joined directly or by an equal CH2-Ch3 group to the other alkylene radical.

United States Patent 191 Rossi et al.

[ June 11, 1974 LUBRICATING COMPOSITEONS INHIBITED FROM OXIDATION [75] Inventors: Enzo Rossi; Silvano Fattori, both of San Donato Milanese, Italy [73] Assignee: Snam Progetti, San Donato,

Milanese, ltaly [22] Filed: Sept. 15, 1972 [2]] Appl. No.: 289,227

[30] Foreign Application Priority Data Sept. 16, 197 1, Italy 287l 1/11 [52] US. Cl 252/482, 252/45, 252/406, 250/329 HS [51] Int. Cl Cl0m 1/38 [58] Field of Search 252/45, 48.2, 406; 260/329 HS, 329 F [56] References Cited UNITED STATES PATENTS 9/l950 Hartough et al 252/45 X 3/1955 Brooks 252/45 Primary Examiner-W. Cannon ABSTRACT A lubricating composition of mineral oil or synthetic oil is inhibited from oxidation by dissolving therein. at temperatures not higher than 80 C, from 0.001 to l0 per cent by weight of a derivative of thio-thiophthene which is represented by the general formula:

6 Claims, N0 Drawings The invention relates to the inhibition of the oxidation of lubricating compositions, achieved through the use of particular additives which have shown extremely valuable advantages with respect to the ones normally used in the art.

It is well known that the high temperatures developed in the modern engines favour the oxidation of lubricants with formation of acid products which cause the corrosion of the metal surfaces with which they come to contact.

Furthermore, said oxidation products deposit either as pitch products or varnish, or as lacquers on said metal surfaces thus causing a decrease of the efficiency of the engine itself. For the purpose of avoiding, as much as possible these undesirable effects from the lubricants the so-called antioxidizer additives are added, such as the sterically hindered phenols, aromatic amines, alkylphenols sulphides, dialkylphosphates of Ca, Ba, and Al and other numerous ones.

But the inconveniences due to oxidation were not actually removed in a satisfactory way.

Therefore it is an object of this invention to supply additives which are inhibitors of oxidation for a wide range of products, such as lubricating compositions containing mineral oils, obtained from the most different raw materials refined through acids or solvents or coming from hydrocracking, said additives being also suitable to inhibit from oxidation lubricating compositions containing synthetic bases, such as synthetic hydrocarbons, synthetic esters, silicones, hydrogenated polyolefins, polyalkylen oxides, alkybenzenes, esters of phosphoric acid, and others.

Now we have found that the above mentioned effects, and others which will become apparent in the course of the present specification, are attained through the utilization of thiothiophthene derivatives, which are adapted to give lubricating compositions on oxidation resistance which is absolutely better than the one obtained with other known oxidation inhibitors.

The thio-thiophthene derivatives may be represented by the following general formula rectly or by an equal GHQ-CH3 group to the other alkylene radical.

Said antioxidizing additives dissolve in the lubricating fluid by heating to a temperature not higher than 70-80 C.

The amount of the derivatives of the thiothiophthene which are used depends or various factors such as the nature of the base and the presence of others additives.

The use of said additives is particularly advantageous since they are efficacious also at very low concentrations, of about 0.01 percent or less. Generally the thiothiophthenes are used in concentrations which range from the 0.001 percent to 10 percent by weight and preferably from the 0.01 to the 5 percent b.w.

' The lubricants containing the antioxidizers of the invention may also contain various other types of addit'ives normally used, like detergents, dispersants corrosion inhibitors and antirust, viscosity index improvers, sludge inhibitors, pour point depressants and also other antioxidizers in the case it were desirable to improve the characteristics of the oxidation inhibition of compositions already containing antioxidizing agents.

The preparation of the thio-thiophthene derivatives of the present invention is generally well known to the people skilled in the art. For instance the methods described by F. Arndt et al. (Chem. Ber. 1925, 58, 1633) and by M. Stawaux and N. Lozach (Bull. Soc. Chim. France, 1967, 2082) may be used.

The method of preparation consists in causing the triketones, dissolved generally in aromatic solvents, to react with P 8 The reaction mass is treated with aqueous NaOl-l and the desired product crystallizes out of the organic phase.

The inventive antioxidizers may also be named as derivatives of thio-thiophthene, and they may also be named as trithio-l,5,6 S pentalenes.

To provide a better understanding of the invention and to demonstrate the advantages of it, the following illustrative examples are reported.

EXAMPLE 1 To a flask with three necks provided with a stirrer and cooler, 10 g of di l-methyl-5-p.methoxyphenyll,3,5-triketone dissolved in 1,000 ml of benzene and 20g of P 8 were fed.

Boiling was maintained during about 2 hours.

After cooling a concentrated solution of NaOH was added and it was stirred for about 15.

At the end the benzene phase was separated.

The residue was subjected to two further extractions with benzene. The benzene extracts were gathered, washed with H 0 and concentrated by evaporating the benzene.

A red brown residue was obtained.

By recrystallizing from ethyl acetate crystals were obtained having a melting point of 219-220 C (observed 221 C). The sulfur content calculated for the C l- 05 product was 34.30 percent; the ones found through analysis was 33.9 percent.

EXAMPLE 2 With the purpose of evaluating the antioxidizing properties of the thio-thiophthene derivatives in lubricating compositions, some tests of oxygen absorption were carried out. Said test was efiected in an apparatus of the type described by G. Miliotis and co-operators (Bull. Soc. Chim. France, 1969; 847) and consisted in determining the induction period of the oxidation of a product maintained under a strong stirring in a reactor provided with a thermostat. The reactor filled with oxygen, was connected with a graduated buret for gases, which was also filled with oxygen.

A differential gauge marked the oxygen absorption. group consisting of mineral and synthetic lubricating The tests were carried out at l60i2C on 10 ml. oil oils, at temperatures not higher than 80 C and in a samples, by using as catalyst copper powder in an quantity ranging from 0.001 to 10 per cent by weight, amount of 50 mg. a derivative of thio-thiophthene represented by the The inventive products were dissolved in paraffinic 5 general formula: mineral oil having a 30 SAE viscosity grade.

The results were reported in table 1. 7

TABLE] R 5 2 R1 Induction l0 4 3 Number of Concentration period/ R2 R3 the test Additive moles/liter minutes v 1 none 14 wherein R, R R and R which may be the same or 2 y y -2 270 different, are members of the group consisting of hy- 3 2126thytinmemoxwhewt -2 638 15 drogen, alkyl, cycloalkyl, aryl, alkylaryl, arylalkyl, al-

thio-thiophthene koxyaryl, alkoxyalkyl and aroxyalkyl, or R and R 4 10-2 662 represent a CH Cit-CH or Cl-l -CH -CH alkylene phenyl-thio-thiophthene radical connecting the number 3 and 4 carbon atoms of the thio-thiophthene molecule. EXAMPLE 3 ,2O 2. Lubricating composition according to claim 1 Through the apparatus and the method described in characterized in that the derivative of the thio-' example 2 the additives of the invention dissolved in thiophthene is 2-methyl-5. methoxyphenyl thiotrimethyl adipate of octyl gave the results reported in thiophthene and is present in an amount in the range I table 2. H of 0.01 to 5 per cent by weight.

TABLE 2 lndustion Number of Additive Concentration period, the test moles/liter minutes l none 4 2 phenyl-a-naphtylam ine 3,5. l()" I24 3 Z-methyI-S-pmethoxyphenylthio-thiophthene 3.5.10 148 4 2,5-di-p,methoxyphenyl-3- phenyl thio-thiophthene 3.5.10 256 5 2,5-diphenyl-thio-thiophthene 3.5.10 220 6 2.5-di-p.methoxyphenyl-3.4-diphenyl-thio-thiophthene 3,5ll0' l9? 7 2,5-diphenyl-3,4-trimethylen thin-thiophthene 3,510 345 The derivatives of thio-thiophthene may be advanta- 4O 3.. Lubricating composition according to claim 1 geously used in oils for engines and for gears, in various characterized in that the derivative of the thiohydraulic fluids and generally transmission fluids, in inthiophthene is 2,5 di p. methoxyphenyl-3-phenyl thiodustrial and marine oils. thiophthene and is present in an amount in the range From tables 1 and 2 it is possible to notice that the of 0.01 to 5 per cent by weight. compounds of the invention are remarkably better than Lubl'lcatlng composition according to Claim 1 well known commercial antioxidizers such as 2,6 Characterized in at the derivative of the thiodi-t butyl-4-methyl phenol and phenyl-a- IhlOPhfl'lCnB 15 2,5 dlPhCIIYI-IhlO-thlOPhthGl'lfi and i5 h h 1 i present in an amount in the range of 0.01 to 5 per cent Said derivatives of thio-thiophthene as already rey ported, particularly prevent the oxidation of various 5O f lg composition according to Claim 1 types of lubricating bases at high temperatures and characterlzeq that the erivative of the thioachieve the purposes of the invention both as above thiophthene 15 5 di P- yp y 'l mentioned from the point of view of a better activity as two-thiophthene and i5 Present in an amount in the antioxidizers with respect to the conventional antioxirange of 001 to 5 P Cent y might dizers, and from the point of view of their flexibility in Lubricating Composition according to Claim 1 use as antioxidizing agents i h already mentioned characterized in that the derivative of the thiorange f lubricating products th ophthene lS 2,5-di-phenyl-3,4-trimethylenethiow claim; thiophthene and is present in an amount in the range 1. A lubricating composition, inhibited from oxidaof to 5 P 9 by W g tion, prepared by dissolving in an oil selected from the it 

2. Lubricating composition according to claim 1 characterized in that the derivative of the thio-thiophthene is 2-methyl-5. methoxyphenyl thio-thiophthene and is present in an amount in the range of 0.01 to 5 per cent by weight.
 3. Lubricating composition according to claim 1 characterized in that the derivative of the thio-thiophthene is 2,5 di p. methoxyphenyl-3-phenyl thio-thiophthene and is present in an amount in the range of 0.01 to 5 per cent by weight.
 4. Lubricating composition according to claim 1 characterized in that the derivative of the thio-thiophthene is 2,5 diphenyl-thio-thiophthene and is present in an amount in the range of 0.01 to 5 per cent by weight.
 5. Lubricating composition according to claim 1 characterized in that the derivative of the thio-thiophthene is 2,5 di p. methoxyphenyl-3,4-diphenyl thio-thiophthene and is present in an amount in the range of 0.01 to 5 per cent by weight.
 6. Lubricating composition according to claim 1 characterized in that the derivative of the thio-thiophthene is 2,5-di-phenyl-3,4-tRimethylene-thio-thiophthene and is present in an amount in the range of 0.01 to 5 per cent by weight. 